<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <style>
    .outer {
      position: relative;
      height: 100px;
    }
    .left,
    .right {
      height: 100%;
    }
    .left {
      position: absolute;
      width: 200px;
      background: tomato;
    }
    .right {
      margin-left: 200px;
      background: pink;
    }
  </style>
  <body>
    <div class="outer">
      <div class="left"></div>
      <div class="right"></div>
    </div>
  </body>
</html>
